The pedicle screw, which is sometimes used as an adjunct to spinal fusion surgery, provides a means of gripping a spinal segment. The screws themselves do not fixate the spinal segment, but act as anchor points that can then be connected with a rod. The screws are usually placed at two or three consecutive spine segments and then a rod is used to connect the screws. A generally yoke-like coupler and a locking device (e.g. set screw) is typically used to compress the rod against (directly or with an intermediate element) the spinal screw head and lock the assembly. Together, the rod, coupler, and screw cooperate to stabilize and generally immobilize the spinal segments that are being fused.
Most screws and couplers are constructed such that the screw has polyaxial movement relative to the coupler prior to being locked into position. The polyaxial screw assembly allows the rod to be placed at a variety of angles relative to the angle at which the screw is placed in the pedicle. The rods and couplers of the devices often coordinate with a device (e.g., set screw) which locks the rod in place and locks the angle and position of the rod relative to the polyaxial screw.
While pedicle screw, rod, and coupler systems have many benefits, there remain challenges and inadequacies. For example, the pedicle screw, coupler, and rod systems are often made up of multiple pieces which can get dropped, fumbled during surgery, or misplaced. The multitude of pieces to a system might also mean that that several people are required to assemble and align the pieces during surgery.
Additionally, the multitude of pieces to a system can also result in a high assembled profile, which can be uncomfortable, if not painful, to a recovering patient. A high profile system can also be disruptive to the recovered patient since the systems are seldom removed once spine fusion is complete.
Furthermore, while the polyaxial nature of the system is a benefit to final alignment, one drawback to a polyaxial screw system is that before the rod is locked down, the coupler and rod can typically move freely relative to the head of the screw as other pedicle screws are implanted and as the rod is connected to another coupler. This makes the actual process of aligning and holding the coupler and rod in place prior to locking down all polyaxial screw systems more complicated—requiring more finesse and potentially multiple operators. These challenges can prolong surgery time and add cost and risk to the procedure and to patient recovery.
Thus, there is a need for pedicle screw and rod devices that are easier to distribute, store, sterilize and/or use. These and other needs are met by embodiments described herein.